TM 9-2520-246-34-1 d. Mainshaft Assembly. FRAME 1 1. Put first and reverse gear (1) into back of transmission case (2) so that grooved collar on first and reverse gear faces front of transmission case. 2. Holding both ends of mainshaft assembly (3) as shown, slide mainshaft assembly through first and reverse gear (1). 3. Let mainshaft assembly (3) rest on countershaft assembly in transmission case (2). GO TO FRAME 2 2-93